Supporting beam deflection switch actuated overload safety device for elevators



United States Patent SUPPORTING BEAM DEFLECTION SWITCH AC- TUATED OVERLOAD SAFETY DEVICE FOR ELEVATORS Gordon M. Harwood, 5210 N. Capitol St. NW., Washington, D.C. Filed Nov. 29, 1963, Ser. No. 326,666 2 Claims. (Cl. 18729) This invention relates to new and useful improvements in safety equipment for elevators, and in particular the invention concerns itself with safety apparatus which is responsive to loading and possible overloading of the elevator car.

The principal object of the invention is to prevent damage to the elevator in general and breakage of the car hoist cables in particular, resulting from overloading of the car beyond its rated capacity.

This object is attained by the provision of a safety device which, when the car is overloaded, automatically interrupts the flow of electric current to the motor of the winch which actuates the hoist cables, so that the car cannot be moved until the overload is eliminated. An important feature of the invention resides in arranging the safety device so that it responds to deflection of the usual transverse supporting beam at the top of the car to which the hoist cables are connected, whereby a highly accurate control and safeguard against overloading damage is attained, as will be hereinafter explained.

Another important feature of the invention resides in the provision of means, responsive to actuation of the usual brake on the hoisting win-ch, for effecting interruption of current to the winch motor only while the brake is applied and the car is overloaded when standing still, so that operation of the motor and winch is not uhduly interrupted as a result of car bouncing incidental to acceleration and deceleration of the car when the normal loading capacity of the car is not exceeded.

Other objects, features and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein like characters of reference are used to designate like parts, and wherein:

FIGURE 1 is a fragmentary elevational view of an elevator embodying the safety device of the invention;

FIGURE 2 is an enlarged cross-sectional detail, taken substantially in the plane of the line 22 in FIGURE 1;

FIGURE 3 is a fragmentary, enlarged elevational view of the overload responsive switch and its mounting on the supporting beam of the elevator car;

FIGURE 4 is a fragmentary sectional view, taken substantially in the plane of the line 4-4 in FIGURE 3;

FIGURE 5 is a diagrammatic illustration, exaggerated to show the deflection of the car supporting beam; and

FIGURE 6 is a wiring diagram of the electrical components of the invention.

Referring now to the accompanying drawings in detail, FIGURE 1 illustrates .a conventional passenger or freight elevator arrangement including an elevator car 10 suspended by suitable frame members 11 from the end portions of a transverse beam assembly 12 at the top of the car, the beam and the car being provided with shoes 13, 14 which slidably engage vertical guides 15 in the elevator shaft. A hoist cable 16 is suitably connected by conventional means 17 to the center of the beam assembly 12 for raising and lowering the car 10, the cable 16 3,241,636 Patented Mar. 22, 1966 being windable upon a winch 18 which is driven through suitable gearing 19 by an electric motor 20. The winch 18 is equipped with a conventional brake, including an external expanding and contracting brake band 21, and while the drawing shows the winch and the motor as being mounted on suitable supporting structure 22 at the top of the elevator shaft, the same may also be positioned in a basement or pit adjacent the bottom of the shaft, as is often the customary practice.

The invention involves the provision of a safety device for preventing damage to the elevator, particularly breakage of the hoist cable 16, when the car 10 is overloaded, such a safety device being fully automatic and operative toprevent operation of the motor driven winch 18, and consequently, movement of the car 10, in the presence of an overload.

Before proceeding to describe the arrangement of the safety device itself, it may be noted that the operation thereof is responsive to a deflection of the beam assembly 12 which takes place when the elevator car is loaded. Since the car 10 is connected to the end portions of the beam assembly 12 by the frame members 11, and since the hoist cable 16 is connected by the means 17 to the center of the beam, it becomes obvious that upon loading of the car the cable 16 will have a tendency to hold up the center of the beam assembly while the weight of the car and the load therein will have the tendency to pull the end portions of the beam assembly downwardly. As a result of these forces acting in opposite directions, the center portion of the beam assembly will become upwardly deflected or arched, the magnitude of this deflection increasing with the weight of the load placed in the car. Considering the fact that the normal capacity of the car may be 3,000 lbs. or more, the center of the beam assembly 12 may be deflected upwardly by as much as .020" or more, this deflect-ion being exaggerated for illustrative purposes in FIGURE 5 wherein the dotted line 23 indicates the beam assembly 12 in a normal or undefiected position when the elevator car is empty, while the solid line 24 indicates the upwardly deflected position of the beam assembly when the car is loaded or overloaded, the dimension indicated by the arrows at 25 representing the magnitude of the beam assembly deflection. It is this deflection of the beam which is utilized to actuate the safety overload device of the invention.

' The safety device comprises a suitable electric switch, preferably a micro-switch 26, which is disposed in a suitable box or housing 27 equipped with a removable cover plate 28. The body of the switch 26 is provided with an externally screw-threaded adapter 29 which extends through an apertured mounting plate 30 and is adjustably secured thereto by a pair of lock nuts 31. The apertured mounting plate 30 is carried by a vertical, screw-threaded shaft or stem 32 which is slidable in vertically aligned openings 33 formed in the box 27, the plate 30 being adjustably secured to the shaft 32 by .a pair of lock nuts 34. The adapter '29 accommodates a vertically slidable switch actuating element 35 which is in engagement with an abutment 36 in the box 27. The switch 26 is normally open, but upward sliding of the shaft 32 in the box 27 will move the switch upwardly 1 so that the actuating element 35 is depressed by the abutment 36 to cause closing of the switch. The switch box 27 is secured by suitable screws 37 to the center por-v tion of an elongated mounting member or strap 38 which is disposed horizontally alongside the beam assembly 12 beam assembly.

and has its ends secured by bolts or screws 39 to the end portions of the beam assembly, as shown in FIG- URE 1. For purposes of explanation it may be noted that the conventional beam assembly 12 may consist of a pair of U-beams 12a, 12b, disposed in spaced, backto-back relation and spanned by upper and lower plates 12c, 12d, to which the cable connecting means 17 are attached. As is best shown in FIGURE 2, the mounting strap 38 is disposed on edge, that is, with its major transverse dimension in a vertical plane, so that its resistance to bending or deflection in that plane is considerable. Moreover, the center portion of the strap 38 is free of connection to the center portion of the beam assembly 12, and consequently, when the center portion of the beam assembly is deflected under load as already explained, the strap 38 will remain straight and free of deflection, notwithstanding the attachment of the ends of the strap by the bolts 39 to the end portions of the In this regard it will be noted that the strap 38 is somewhat narrower than the space between the flanges of the adjacent U-beam 12a, so as to provide clearance for deflection of the beam assembly without alfecting the straightne'ss of the strap, as will be clearly apparent from FIGURE 2.

Since the switch box 27 is secured to the center portion of the mounting strap 38, it will remain relatively stationary while the beam assembly 12 is deflected under load. However, the upper end portion of the shaft 32 extends through an aperture 40 in the beam assembly and is adjustably secured therein by a pair of locknuts 41, so that when the beam assembly is subjected to upward deflection as explained, the shaft 32 will be caused to slide upwardly in the box 27 to eflectclosing of the switch 26. Conversely, when the elevator car is unloaded, the beam assembly will return to its initial straight position and downward sliding of the shaft 32 in the box 27 will cause the switch 26 to open.

The switch 26 is connected in series with a relay 42 to a suitable source of current 43, the relay 42 in turn, being operative to open and close the main elevator circuit 44 which supplies current to the winch motor 20. The relay 42 is normally closed when the switch 26 is open, so as to make operation of the motor 20 possible. However, closing of the switch 26 actuates the relay 42 so as to interrupt the flow of current to the motor, from which it will be apparent that when the elevator car is loaded to a point of overload which causes a predeter mined magnitude of deflection of the beam assembly 12 suflicient to close the switch 26, opening of the relay will automatically interrupt the current flowing to the winch motor 20, so that movement of the elevator car will not be possible until such time as the overload in the car is removed and deflection of the beam assembly 12 subsides to a lesser magnitude at which the switch 26 becomes opened.

However, a situation occurs during acceleration and deceleration of the elevator car when the car is subjected to a certain amount of upward and downward bouncing, which may also produce a deflection of the beam assem bly even when the' car is not overloaded. The beam assembly deflection incidental to such bouncing would unduly cause the safety device to interrupt flow of current to the hoist or winch motor while the car is still moving, which of course would be undesirable. Accordingly, the invention provides another switch, preferably a micro-switch 45, which is mounted adjacent the aforementioned brake band 21 of the winch 18 and is normally open when the brake is released and the elevator car is in motion. The switch 45 is connected in series with the switch 26 and the relay 42 to the current source 43, and when the brake 21 is off during movement of the elevator car, the normally open switch 45 prevents interruption of current to the winch motor by the relay 42 even when the switch 26 is closed by deflection of the beam assembly 12 incident to acceleration or deceleration of the car. Nevertheless, when the brake 21 is applied and the switch 45 is closed by the application of the brake, closing of the switch 26 by deflection of the beam assembly under overload will automatically interrupt the current to the winch motor, as will be clearly understood.

Signalling means are provided to indicate to the operator of the elevator car when the car is overloaded. Such means may be either audible or visible, and for illustrative purposes the same are represented in the drawings by a signal lamp 46 mounted in a housing 47 inside the car 10, the housing carrying a legend or indicia such as overload, which is illuminated by the lamp on the appropriate occasion. The lamp 46 is connected in parallel with the relay 42 to the current source 43 so that the lamp is energized concurrently with actuation of the relay, as already explained.

The switch 26 in the box 27 on the beam assembly 12 is connected by conductor means 48 to a junction box 49 at the underside of the car 10, a branch 48a extending from the conductor means 48 to the lamp 46 a in the housing 47. A drop cable 50 extends from the box 49 to another connector box 51 located halfway up the elevator shaft, and connection is made from the boX 51 by a conductor 52 to the switch 45 and also to the relay 42 which is usually located on an electrical panel (not shown) adjacent the motor 20.

While in the foregoing there has been described and shown the preferred embodiment of the invention, vari ous modifications may become apparent to those skilled in the art to which the invention relates. Accordingly, it is not desired to limit the invention to this disclosure, and various modifications and equivalents may be resorted to, falling within the spirit and scope of the invention as claimed.

What is claimed as new is:

1. In an elevator, the combination of a horizontally disposed elevator car supporting beam having a car suspended therefrom and subject to vertical deflection under car load, said beam comprising an open-sided channel including a vertical web and upper and lower horizontal flanges projecting laterally .to one side from the respective upper and lower edges of said web, and an overload safety switch mechanism comprising a horizontally elongated vertically disposed mounting strap juxtaposed to said web of said channel and .secured at its ends only to said web whereby the strap may remain horizontal when the beam is subjected to vertical deflection, a switch housing secured to the center portion of said mounting strap and disposed wholly within said channel, a vertical stem secured at its upper end to the upper flange of the channel and extending slidably downwardly through said switch housing, a portion of said stem within the switch housing being screw-threaded, a mounting plate vertically adjustably positioned on the screw-threaded portion of said stem in said switch housing and projecting laterally from the stem, a micro-switch movably positioned in said switch housing and having a screw-threaded mounting adapter vertically adjustably secured in an opening in said mounting plate and also having a vertically slidable switch actuating element projecting 11p wardly from said adapter, a rigid abutment member provided in said switch housing in engagement with said actuating element of said switch whereby said switch may be actuated by vertical movement thereof with said stem relative to said switch housing and mounting strap when said beam is vertically deflected, and electrical overload indicating means in circuit with said switch.

2. The combination as defined in claim 1 wherein said elevator also includes a winch brake having a movable brake applying member, and a brake actuated switch responsive to movement of said brake applying member and connected in series with said first mentioned switch whereby said indicating means may be energized by said first mentioned switch only when the winch brake is References Cited by the Examiner STATES PATENTS Staley 18729 Turner 18729 Green 187-29 Borovec 18729 Doolan 187-29 Bruns et a1. 187-29 Staley 187-29 Beck 18729 Drexler I 18729 Tressel 18729 MILTON O. HIRSHFIELD, Primary Examiner. 

1. IN AN ELEVATOR, THE COMBINATION OF A HORIZONTALLY DISPOSED ELEVATOR CAR SUPPORTING BEAM HAVING A CAR SUSPENDED THEREFROM AND SUBJECT TO VERTICAL DEFLECTION UNDER CAR LOAD, SAID BEAM COMPRISING AN OPEN-SIDED CHANNEL INCLUDING A VERTICAL WEB AND UPPER AND LOWER HORIZONTAL FLANGES PROJECTING LATERALLY TO ONE SIDE FROM THE RESPECTIVE UPPER AND LOWER EDGES OF SAID WEB, AND AN OVERLOAD SAFETY SWITCH MECHANISM COMPRISING A HORIZONTALLY ELONGATED VERTICALLY DISPOSED MOUNTING STRAP JUXTAPOSED TO SAID WEB OF SAID CHANNEL AND SECURED AT ITS ENDS ONLY TO SAID WEB WHEREBY THE STRAP MAY REMAIN HORIZONTAL WHEN THE BEAM IS SUBJECTED TO VERTICAL DEFLECTION, A SWITCH HOUSING SECURED TO THE CENTER PORTION OF SAID MOUNTING STRAP AND DISPOSED WHOLLY WITHIN SAID CHANNEL, A VERTICL STEM SECURED AT ITS UPPER END TO THE UPPER FLANGE OF THE CHANNEL AND EXTENDING SLIDABLY DOWNWARDLY THROUGH SAID SWITCH HOUSING, A PORTION OF SAID STEM WITHIN THE SWITCH HOUSING BEING SCREW-THREADED, A MOUNTING PLATE VERTICALLY ADJUSTABLY POSITIONED ON THE SCREW-THREADED PORTION OF SAID STEM IN SAID SWITCH HOUSING AND PROJECTING LATERALLY FROM THE STEM, A MICRO-SWITCH MOVABLY POSITIONED IN SAID SWITCH HOUSING AND HAVING A SCREW-THREADED MOUNTING ADAPTER VERTICALLY ADJUSTABLY SECURED IN AN OPENING IN SAID MOUNTING PLATE AND ALSO HAVING A VERTICALLY SLIDABLE SWITCH ACTUATING ELEMENT PROJECTING UPWARDLY FROM SAID ADAPTER, A RIGID ABUTMENT MEMBER PROVIDED IN SAID SWITCH HOUSING IN ENGAGEMENT WITH SAID ACTUATING ELEMENT OF SAID SWITCH WHEREBY SAID SWITCH MAY BE ACTUATED BY VERTICAL MOVEMENT THEREOF WITH SAID STEM RELATIVE TO SAID SWITCH HOUSING AND MOUNTING STRAP WHEN SAID BEAM IS VERTICALLY DEFLECTED, AND ELECTRICAL OVERLOAD INDICATING MEANS IN CIRCUIT WITH SAID SWITCH. 